Citation: Su, H.; Pan, M.-S.; Mai,
H.-W. QoS-Aware Downlink Traffic
Scheduling for Cellular Networks
with Dual Connectivity. Electronics
2022, 11, 3085. https://doi.org/
10.3390/electronics11193085
Academic Editors: Alexandros-
Apostolos Boulogeorgos, Panagiotis
Sarigiannidis, Thomas Lagkas,
Vasileios Argyriou and Pantelis
Angelidis
Received: 30 August 2022
Accepted: 22 September 2022
Published: 27 September 2022
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Article
QoS-Aware Downlink Traffic Scheduling for Cellular Networks
with Dual Connectivity
Haoru Su
1
, Meng-Shiuan Pan
2,
* and Hung-Wei Mai
3
1
Department of Software Engineering, Faculty of Information Technology, Beijing University of Technology,
Beijing 100021, China
2
Department of Electronic Engineering, National Taipei University of Technology, Taipei 10608, Taiwan
3
Department of Computer Science and Information Engineering, Tamkang University,
New Taipei City 251301, Taiwan
* Correspondence: mspan@ntut.edu.tw
Abstract:
In a cellular network, how to preserve users’ quality of service (QoS) demands is an
important issue. To provide better data services, researchers and industry have discussed the de-
ployment of small cells in cellular networks to support dual connectivity enhancement for user
equipments (UEs). By such an enhancement, a base station can dispatch downlink data to its sur-
rounding small cells, and UEs that are located in the overlapping areas of the base station and
small cells can receive downlink data from both sides simultaneously. We observe that previous
works do not jointly consider QoS requirements and system capabilities when making scheduling
decisions. Therefore, in this work, we design a QoS traffic scheduling scheme for dual connec-
tivity networks. The designed scheme contains two parts. First, we propose a data dispatching
decision scheme for the base station to decide how much data should be dispatched to small cells.
When making a dispatching decision, the proposed scheme aims to maximize throughput and ensure
that data flows can be processed in time. Second, we design a radio resource scheduling method,
which aims to reduce dropping ratios of high-priority QoS data flows, while avoiding wasting radio
resources. In this work, we verify our design using simulation programs. The experimental results
show that compared to the existing methods, the proposed scheme can effectively increase system
throughput and decrease packet drop ratios.
Keywords: cellular networks; dual connectivity; small cell; scheduling; quality of service (QoS)
1. Introduction
The popularity of wireless networks facilitates the development of various mobile
applications, e.g., e-health care [
1
] and augmented reality (AR)/virtual reality (VR) [
2
].
People are used to enjoying these mobile services in their daily lives, and thus, the demands
on the capacity and quality of mobile networks are still increasing. To provide broadband
downlink data services, most countries have constructed 4G/5G cellular network systems
specified by the third Generation Partnership Project (3GPP). In a 4G/5G cellular network,
each user equipment (UE) will connect to a master evolved Node B (MeNB), i.e., the base
station. The MeNB is responsible for assigning radio resources to UEs that connect to it.
Furthermore, researchers and industry have discussed the deployment of small cells in
cellular networks. Small cells are taken as secondary evolved Node B (SeNBs), which can
provide dual connectivity enhancements for UEs. By such an enhancement, a UE that is
located in the overlapping area of the MeNB and a SeNB can obtain radio resources from
both sides simultaneously. In other words, UEs can receive more downlink data from both
MeNB and SeNB, and thus the network capacity can be increased.
Figure 1 shows the protocol stack of the cellular network with dual connectivity en-
hancement defined in 3GPP specification 36.300 [
3
]. In this architecture, layer 1 is the
physical layer (PHY). Layer 2 contains a media access control sublayer (MAC), radio link
Electronics 2022, 11, 3085. https://doi.org/10.3390/electronics11193085 https://www.mdpi.com/journal/electronics
